Comparison of plantar deformation and damping behavior in different areas of plantar tissue in relaxed and tense muscular state

Abstract During gait, the cushioning function of the soft tissue on the sole of the foot plays a pivotal role, which is particularly evident when this function is limited due to the lack of these complex structured fat tissue chambers. Therefore, further research of the biomechanics of this tissue is conducted. A technique to determine the effective Young's modulus, the spring constant, and the absorbed energy during impact on the sole of the foot is used to investigate these parameters at four different plantar measurement points. Vertical in vivo impact tests and ultrasonic tissue examinations were used on the right feet of n = 19 study participants for this purpose. Measurements were conducted under the calcaneus, under the first metatarsal head, in the area between the fourth and fifth metatarsal head, and the plantar section of the tendon of the flexor hallucis longus. Measurements were taken both in a relaxed and in a tense muscular state in order to gain insights into the relationship between plantar elasticity and muscular activity. The effective Young's modulus showed a significant (P from 0.0442 to > 0.001) increase at all points in the tense state, while the spring constant rose at just three. Energy absorption decreased significantly (P between 0.04 and 0.002) at all points except for the subcalcaneal region. This provided information may help for further understanding of foot biomechanics and in the development of new tailored damping systems for shoes or insoles.